SODA-LIME-SILICATE GLASS COMPOSITION

Abstract

The invention relates to a clear glass composition of the soda-lime-silicate type that absorbs ultraviolet radiation, which composition includes optical absorbents below in contents varying within the following weight limits: Fe2O3 (total iron) 0.01 to 0.15% V2O5 (total vanadium) 0.11 to 0.40% MnO (total manganese) 0.05 to 0.40% and which has, for a thickness of 3 mm, an ultraviolet transmission not exceeding 40% and chromatic coordinates (a*,b*) of between -3 and 3. It also relates to glass hollowware or flat articles, obtained from the aforementioned composition.

Full Text

SODA-LIME-SILICATE GLASS COMPOSITION
The present invention relates to a soda-lime-silicate
glass composition intended for the production of
articles, particularly glass hollowware, or else those
in the form of sheets of flat glass, the said
composition giving these said articles the following
properties: low transmission of ultraviolet radiation,
high transmission of visible radiation, and neutral
colour.
Although the invention is not limited to such an
application, it will be more particularly described
with reference to applications in the field of glass
hollowware, such as bottles, flasks or pots.
Ultraviolet radiation (UV), in particular solar radiation, may interact with many liquids and sometimes
degrade their quality. This is for example the case

with certain consumable liquids, including certain
wines, spirits, beer or olive oil, the colour and the
taste of which may be impaired, or else certain
perfumes, the aroma of which may be modified. There is
therefore a real need, both in the agri-foodstuffs
industry and the cosmetics industry, for glass
containers capable of absorbing most of the ultraviolet
radiation.
Glass containers meeting this constraint are extremely
commonplace, but in general they are strongly coloured.
Wine and beer are for example often contained in brown
or green bottles, such colorations being obtained by
the addition of pigments such as chromium oxide or
sulphides of transition elements, such as iron
sulphides.. However, these tinted containers have the
drawback of masking the coloration of the liquid that
they contain.
In certain cases, it may be desirable, mainly for

aesthetic reasons, to be able to fully appreciate the
coloration of the contents, and therefore to have
containers of both a high light transmission and a
neutral tint.
Solutions intended to solve this technical problem have
been described, these generally consisting in adding to
a glass composition oxides that preferably absorb
ultraviolet radiation, such as cerium oxide or vanadium
oxide.
Publication US 6 407 021 thus discloses containers made
of glass whose composition comprises 0.2 to 1 wt%
cerium oxide expressed in CeO2 form and 0.01 to
0.08 wt% manganese oxide expressed in MnO2 form. The
latter oxide is added so as to compensate for the
green-yellow tint due to the iron oxide contained in
the composition with a content of at least 0.01%.
Application JP 11-278863 also discloses the use of cerium
oxide, in mass content between 0.1 and 1%, and also cobalt
and, optionally, selenium oxide, the addition of the
latter two compounds also having the effect of
"decolorizing" the glass, that is to say compensating for
the yellow tint provided by the cerium.
The main drawback of cerium oxide is its relatively low
efficiency in absorbing ultraviolet radiation, which
means that it is often necessary to use contents of
greater than 0.5 wt%. Furthermore, a person skilled in
the art knows that cerium, alone or in combination with
certain compounds such as vanadium oxide, gives the
glass "solarization" properties, this term meaning
changes in tint undergone by the glass when it is
exposed to high-energy radiation, such as ultraviolet
radiation.
Vanadium oxide is a useful substitute for cerium oxide,

as its absorptivity for UV radiation is much greater
than that of cerium oxide. However, it may exhibit an
undesirable green coloration, which means the addition
of "decolorizing" oxides.
Application WO 00/35819 discloses the use of vanadium
oxide and phosphorus oxide, the vanadium oxide content
being less than 0.3% expressed as a percentage by
weight.
Application WO 02/066388 discloses compositions
containing small amounts of vanadium and manganese
oxides, with contents of between 0.04 and 0.10% and
between 0.04 and 0.13% respectively, the V2O5/MnO ratio
being between 0.6 and 1.7. However, and even though
manganese oxide is described as acting as a bleacher,
especially through the Mn3+ ion, the glasses exemplified
in that document have dominant wavelengths, generally
of around 560 to 570 nm, demonstrating a slightly
yellow or amber tint. The absorption of ultraviolet by
the glasses disclosed in the examples is characterized
by a transmission of between 1 and 7% at a wavelength
of 330 nm.
Application JP-A-52-47812 also discloses glasses
containing small amounts of vanadium oxide and
manganese oxide, but it considers it to be necessary to
add cerium oxide (with a content of at least 0.15%) and
selenium oxide (at least 0.004%, i.e. 40 ppm, for this
colouring compound is a high content).
The object of the present invention is to propose a
soda-lime-silicate glass composition that can be used
to form glass hollowware possessing a low ultraviolet
transmission, a high transmission in the visible
wavelengths and a neutral tint, so that the appearance
of their contents can be seen perfectly, while still
protecting the organoleptic characteristics of the said

contents.
These objects are achieved according to the present
invention by the glass composition which includes the
following optical absorbents in contents varying within
the following weight limits:
Fe2O3 (total iron) 0.01 to 0.15%;
V2O5 0.11 to 0.40%;
MnO 0.05 to 0.40%,
the glass having the said composition being furthermore
characterized, for a thickness of 3 mm, by an
ultraviolet transmission (Tuv) of less than 40% and a
neutral colour defined by the colorimetric coordinates
a* and b*, each of which is between -3 and +3.
V2O5 and MnO represent the total contents of vanadium
oxide and manganese oxide respectively.
The ultraviolet transmission (Tuv) of the glass
according to the invention is calculated for a
thickness of 3 mm, based on an experimental spectrum
measured, using the solar spectral distribution defined by Parry Moon (J. Franklin Institute, Volume 230,
pp 583-617, 1940) for an air mass 2 and within the
wavelength range from 295 to 380 nm.
The Tuv of the glass according to the invention
preferably does not exceed 30%, especially does not
exceed 25%, or even 20%.
The glass falling within the context of the present
invention is glass of neutral tint, that is to say it
has a transmission curve which varies hardly with the
visible wavelength.
In the CIE (Commission Internationale de l'Eclairage)
system, bodies that are ideally neutral (or grey) do
not possess a dominant wavelength and their excitation

purity is zero. By extension, the body is generally
accepted as being grey if its curve is relatively flat
in the visible range but does have, however, weak
absorption bands that allow a dominant wavelength and a
low, but non-zero purity to be defined.
The glass according to the invention is defined
hereafter by its chromatic coordinates L*, a* and b*
calculated from an experimental spectrum for glass
specimens 3 mm in thickness, taking as reference the
"CIE 1931" reference observer and the standard
illuminant C, both being defined by the CIE. Using this
notation, a body having a neutral coloration is
characterized by a pair of parameters (a*,b*) close to
(0,0) . The glass according to the invention is defined
as having the following:
a* varies from -3 to +3
b* varies from -3 to +3.
Glass having an even greater neutrality is preferably
characterized by an a* value of preferably between -2
and +2, especially between -1 and +1, and by a b* value
of preferably between 0 and +3. The slightly positive
b* values correspond in fact to glass having a slight
yellow coloration, which ensures better colour
rendering than a bluish coloration characterized by
negative b* values.
The use of the aforementioned optical absorbents within
the limits of the invention makes it possible to give
the glass the desired properties and also to optimize
its optical and energy properties.
The action of the absorbents taken individually is in
general well described in the literature.
The presence of iron in a glass composition may result
from the batch materials, as impurities or from

deliberate addition for the purpose of colouring the
glass. It is known that iron exists in the structure of
the glass in the form of ferric ions (Fe3+) and ferrous
ions (Fe2+) . The presence of Fe3+ ions gives the glass a
slight yellow coloration and allows the ultraviolet
radiation to be absorbed. The presence of Fe2+ ions
gives the glass a more pronounced green-blue coloration
and causes infrared radiation to be absorbed.
Increasing the content of iron in both its forms
increases the absorption of radiation at the extremes
of the visible spectrum, this effect taking place to
the detriment of the light transmission.
In the present invention, the total iron content in the
composition is between 0.01 and 0.15%, preferably
between 0.02 and 0.10%. An iron content of less than
0.01% means that the batch materials must have a high
degree of purity, which results in too high a cost of
the glass for use as bottles or flasks. Above 0.15%
iron, the glass composition has too low a transmission
in the visible range and an excessively pronounced
green tint.
Vanadium oxide exists in three oxidation states in the
glass. The V5+ ion is responsible for ultraviolet
absorption, whereas the V4+ and V3+ ions give an
undesirable green coloration. Within the context of the
present invention, and so as to obtain the desired UV
transmission values, the total vanadium oxide content
expressed in V2O5 form is necessarily not less than
0.11%, preferably not less than 0.13%, or even 0.15 or
0.16%, especially not less than 0.20%, and even more
preferably not less than 0.25%. For reasons essentially
due to the high cost of vanadium oxide, the content of
the latter is preferably less than 0.40%, especially
less than 0.30% and even less than 0.28%. Vanadium
oxide contents of between 0.11 and 0.17% generally give
glass having a Tuv of around 20 to 40%, whereas amounts

that are greater than or equal to 0.17%, or even 0.19%,
are often needed to ensure a Tuv of less than 20%. A
vanadium oxide content of between 0.19 and 0.22% aims
in this case to be particularly suitable.
Manganese oxide exists in the glass in oxidized form
(Mn3+)and reduced form (Mn2+. Whereas the reduced form
produces only a very slight coloration, Mn3+ ions give
the glass containing them an intense pink or violet
coloration. As is well known to those skilled in the
art, this form is particularly useful for compensating
for the green tint attributable to iron oxide and, in
the case of the present invention, to vanadium oxide.
The inventors have nevertheless demonstrated an
additional and unexpected beneficial effect . of
manganese oxide on the UV transmission when this is
used in combination with vanadium oxide. It has been
discovered that the addition of manganese oxide makes
it possible to reduce the vanadium oxide content needed
to achieve a given Tuv, or even to reduce the Tuv, of a
glass containing a given amount of vanadium oxide.
Consequently, the glass according to the invention has
an MnO content (representing the total content of
manganese oxide) not less than 0.05%, preferably not
less than 0.09%, or even 0.10%, and even more
preferably not less than 0.13%. For the reasons
mentioned above, the MnO contents are sometimes
advantageously greater than 0.15%, especially greater
than 0.18% and even greater than 0.20%. To avoid the
appearance of an undesirable pink or violet coloration,
the MnO content is kept at 0.40% or less, preferably
0.25% or less, or even 0.22% or less.
The inventors have also discovered that the optimized
proportion of MnO to be introduced relative to the
amount of vanadium oxide in order to achieve a neutral
coloration varies according to the method employed for
adding the optical absorbents, and especially according

to the temperature which this method is carried out at.
When the addition of the vanadium and manganese oxides
or of manganese oxide alone is carried out in the
melting furnace using the "tank coloration" method,
usually within a temperature range from 1400°C to
1500°C, the ratio R1, defined by the weight content of
manganese oxide relative to the weight content of
vanadium oxide, is preferably chosen to be between 1.2
and 1.8, and especially to be not less than 1.5. When the
addition of these oxides or of manganese oxide alone is
carried out in a feeder for transporting the glass from
the furnace to the forming devices, usually at
temperatures of around 1200°C to 1300°C, this ratio Rl is
preferably chosen to be not less than 0.5, or even 0.8,
but to not exceed 1.2, or even 1.0. Especially in the case
of feeder addition of the manganese and vanadium oxides or
of manganese oxide alone, the combination of a vanadium
oxide content of between 0.19 and 0.22% with a manganese
oxide content of between 0.13 and 0.18% is particularly
preferred. In general, and irrespective of the way in
which the manganese and vanadium oxides are introduced,
the ratio Rl must be increased if the glass has too low an
a* value and must be decreased if the glass has too high
an a* value.
Cobalt oxide produces an intense blue coloration and so
reduces the light transmission. Its role in the present
invention is to compensate for any yellow component
caused by an excessive Mn3+ ion content. The amount must
therefdre be perfectly controlled in order to make both
the light transmission and the coloration compatible
with the use to which the glass is intended. According
to the invention, the cobalt oxide content preferably does not exceed 0.0025%, preferably does not exceed
0.0020%, or does not exceed 0.0015% even does not
exceed 0.0010%. This is because above 0.0025% the light
transmission of the glass becomes too low, and the tint
becomes too blue.

Within the context of the present invention, a
particularly preferred composition, in particular when
vanadium and manganese oxides are introduced in the
tank, includes the following optical absorbents in a
content varying within the following weight limits:

Another preferred embodiment, in particular when the
vanadium and manganese oxides or the manganese oxide
alone, are added in the feeder, consists in choosing
the following composition ranges:

As a general rule, it is difficult to predict the
optical and energy properties of a glass when it
contains several optical absorbents. This is because
such properties result from a complex interaction
between the various absorbents, the behaviour of which
is furthermore dependent on their oxidation state. This
is particularly so in the case of compositions
according to the invention, which contain at least
three oxides existing in several valence states.
in the present invention, the choice of optical
absorbents, their content and their oxidation/reduction
state are key factors for obtaining the required
optical properties.
In particular, the redox state defined by the ratio of
the molar content of ferrous oxide (expressed as FeO)

to the molar content of total iron (expressed as Fe2O3) ,
is less than 0.2, preferably less than or equal to 0.1.
The redox state is generally controlled using oxidizing
agents, such as sodium sulphate, and reducing agents,
such as coke, the relative contents of which are
adjusted in order to obtain the desired redox state.
The oxidized forms of vanadium and manganese may also
fulfil an oxidizing role with respect to ion oxide,
which makes it particularly complicated, or even
impossible, to predict the optical properties of a
glass resulting from a given batch mix.
The composition according to the invention makes it
possible to obtain a glass that preferably has an
overall light transmission LTC calculated, for a
thickness of 3 mm, from an experimental spectrum,
taking the "CIE 1931" reference observer and the
standard illuminant C as reference, that is not less
than 70%, especially not less than 80%, thereby
allowing the desired transparency effect to be
obtained.
The term "soda-lime-silicate" is used here in the
widest sense and relates to any glass composition
consisting of a glass matrix that comprises the
following constituents (in percentages by weight):

It should be mentioned here that the soda-lime-silicate
glass composition may include, apart from the

inevitable impurities contained in particular in the
batch materials, a small proportion (up to 1%) of
further constituents, for example agents for promoting
the melting or refining of the glass (SO3, Cl, Sb2O3,
AS2O3) , or coming from possible addition of recycled
cullet into the batch mix.
In the glass according to the invention, the silica
content is generally maintained within narrow limits
for the following reasons. Above 75%, the viscosity of
the glass and its ability to devitrify increase
greatly, which makes it more difficult to melt and flow
on the bath of molten tin. Below 64%, the hydrolytic
resistance of the glass rapidly decreases and the
transmission in the visible also decreases.
Alumina (Al2O3) plays a particularly important role in
the hydrolytic resistance of the glass. When the glass
according to the invention is intended to form
hollowware containing liquids, the alumina content is
preferably not less than 1%.
The alkali metal oxides Na2O and K2O facilitate the
melting of the glass and allow its viscosity to be
adjusted at high temperatures so as to keep it close to
that of a standard glass. K2O may be used up to 5%, as
the problem of the high cost of the composition rises
above this content. Moreover, the increase in
percentage of K2O can be accomplished, essentially,
only to the detriment of Na2O, which contributes to
increasing the viscosity. The sum of the Na2O and K2O
contents, expressed as percentages by weight, is
preferably not less than 10% and advantageously does
not exceed 20%. If the sum of these contents is greater
than 20% or if the Na2O content is greater than 18%,
the hydrolytic resistance is greatly reduced.
Alkaline-earth oxides allow the viscosity of the glass

to be adapted to the production conditions.
MgO may be used up to about 10% and its omission may be
at least partly compensated for by an increase in the
Na2O and/or SiO2 content. Preferably, the MgO content is
less than 5% and particularly advantageously less than
2%, which has the effect of increasing the infrared
absorptivity without impairing the transmission in the
visible. Low MgO contents furthermore make it possible
to reduce the number of batch materials needed for
melting the glass.
BaO allows the light transmission to be increased and
can be added to the composition in a content of less
than 5%.
BaO has a much less pronounced effect than CaO and MgO
on the viscosity of the glass, and the increase in its
content is essentially accomplished to the detriment of
the alkali metal oxides, of MgO and above all of CaO.
Any BaO increase helps to increase the viscosity of the
glass at low temperatures. Preferably, the glasses
according to the invention contain no BaO.
Apart from complying with the limits defined above as
regards the variation in the content of each alkaline-
earth metal oxide, it is preferable, in order to
achieve the desired transmission properties, to limit
the sum of the weight percentages of MgO, CaO and BaO
to a value of 15% or less.
The composition according to the invention may
furthermore include additives, for example agents that
absorb in certain spectral regions, such as oxides of
transition elements (such as Cr2O3, TiO2, NiO, CuO etc.)
or rare earth oxides (such as CeO2, La2O3, Nd2O3, Er2O3
etc.) or else colouring agents in the elemental state
(Se, Ag, Cu) . The content of such additives is less

than 2%, preferably less than 1%, and even less than
0.5%, or indeed zero (apart from inevitable
impurities). It is particularly preferable for the
glass according to the invention to contain no rare
earth oxides, and especially no neodymium oxide, which
is extremely expensive, and/or no cerium oxide, which
may cause glass with a low iron content to suffer a
solarization effect, the glass becoming brown under the
action of high-energy radiation, such as UV radiation.
The selenium content is also advantageously zero, this
oxide having a strong tendency to volatilize during
melting of the glass, requiring expensive
decontamination equipment.
The glass composition according to the invention is
able to be melted under the production conditions for
glass intended for forming hollowware or flat articles
using the pressing, blowing or moulding techniques, or
even drawing, rolling or floating techniques. Melting
generally takes place in flame-fired furnaces,
optionally provided with electrodes for heating the
glass in the bulk, by passing an electric current
between the two electrodes. To facilitate the melting
operation, and especially to make the latter
mechanically advantageous, the glass composition
advantageously has a temperature corresponding to a
viscosity η such that logη = 2 that is less than
1500°C. Also preferably, the temperature corresponding
to the viscosity η such that logη = 3.5 (denoted by
T(logη = 3.5)) and the liquidus temperature, (denoted
by Tliq) , satisfy the equation:

and better still:

The addition of optically absorbent oxides may be
carried out in the furnace (the process is then
referred to as "tank coloration") or in the feeders

that transport the glass between the furnace and the
forming installations (the process is then referred to
as "feeder coloration"). Feeder coloration requires a
particular addition/mixing installation, but does have,
however, advantages as regards flexibility and
reactivity that are particularly desirable when the
production of an extended range of particular optical
properties and/or tints is required. In the particular
case of feeder coloration the optical absorbents are
incorporated in glass frits or agglomerates, which are
added to a clear glass in order to form, after
homogenization, a glass according to the invention.
Different frits can be employed for each added oxide,
but it may be advantageous in certain cases to use a
single frit containing all the useful optical
absorbents. It is desirable for the vanadium oxide
content or the manganese oxide content in the frits or
agglomerates employed to be between 15 and 25% so as
not to exceed levels of frit dilution in the molten
glass greater than 2%. This is because above 2% is
becomes difficult for the molten glass to be suitably
homogenized, while still maintaining high output
compatible with a low overall economic cost of the
process. It has also been observed that the oxidation
state of the vanadium and of the manganese within the
frits plays a not insignificant role in determining the
redox state of the final glass. Oxidized frits,
therefore those containing vanadium or manganese ions
predominantly in their highest oxidation state, allow
the preferred redox states after mixing to be obtained
more easily, and consequently it is preferable to
employ such frits. Likewise, an oxidizing character of
the flames produced above the glass melt contained in
the feeder is preferred, it being possible to achieve
this by adjusting the inflow of oxidizer relative to
the fuel, such that the oxidizer is supplied
superstoichiometrically. When the oxidizer is oxygen
(O2) and the fuel is methane (CH4) , the O2/CH4 molar

ratio is preferably not less than 2, especially not
less than 2.1 or even 2.2. According to a preferred
embodiment, only vanadium oxide is added in the tank,
the manganese oxide being added in the feeder, in the
form of frits or agglomerates.
The present invention will be more clearly understood
on reading the detailed description below of non-
limiting illustrative examples and the figures appended
hereto:
• Table 1 illustrates various glass compositions
according to the invention;
• Table 2 illustrates the effect of the ratio R1
of the weight content of manganese oxide to the weight
content of vanadium oxide;
• Figure 1 illustrates the additional effect of
manganese oxide on the Tuv when it is employed in
combination with vanadium oxide.
Examples of glass compositions given below (in Tables 1
and 2) allow the advantages associated with the present
invention to be more fully appreciated.
These examples indicate the values of the following
optical properties calculated, for a glass thickness of
3 mm, from experimental spectra:
the ultraviolet transmission (Tuv) calculated
using the solar spectral distribution defined by Parry
Moon (J. Franklin Institute, Volume 230, pp 583-617,
1940) for an air mass 2 and within the wavelength range
from 295 to 380 nm;
the overall light transmission factor (LTC) ,
calculated between 380 and 780 nm, and also the
chromatic coordinates L*, a* and b* . These calculations
were made using the illuminant C as defined by the
ISO/CIE 10526 standard and the CIE 1931 colorimetric
reference observer, as defined by the ISO/CIE 10527
standard.

Also indicated in Tables 1 and 2 are:
the weight contents of iron oxide, vanadium
oxide, manganese oxide and cobalt oxide;
when it was measured, the redox state defined
as the molar ratio of FeO to the total iron expressed
in Fe2O3 form. The total iron content was measured by
X-ray fluorescence and the FeO content was measured by
wet chemistry;
the ratio R1, equal to the mass content of
manganese oxide compared to the mass content of
vanadium oxide.
Each of the compositions given in Tables 1 and 2 was
produced from the following glass matrix, the contents
of which are given in percentages by weight, the
composition being corrected as regards silica in order
to accommodate the total content of colouring agents
added:

Glass compositions 1 to 8 according to the invention,
described in Table 1 were prepared by adding optical
absorbents using a tank coloration method. They
illustrate the important effect of vanadium oxide
coupled with manganese oxide on the Tuv. Comparative
Example 1 is a standard clear glass composition used
both for hollow glassware and for flat glass. Its Tuv
which exceeds 90%, is lowered to about 40% by adding
0.11% vanadium oxide, and then down to 20% by adding
larger amounts. Examples 6, 7 and 8 illustrate the
effect of cobalt oxide, which serves to adjust the b*
value in order to obtain, if desired, a slightly bluish

tint. It may also be noted that these compositions,
which have an R1 ratio close to 1.5, are more neutral
than compositions 3, 4 and 5, which have an Rl ratio
close to 1. The highest neutrality is characterized in
particular by a* values closer to zero. This point
illustrates the importance within the context of the
present invention, of the R1 ratio. Example 1 shows
that the V2O5 content of the glass compositions
according to the invention must necessarily not be less
than 0.11% in order to obtain an ultraviolet
transmission of 40% or less.

The examples given in Table 2 also illustrate the
importance that the R1 ratio can have on the optical
properties, depending on the method in which the
optically active materials were added.
The two examples given (Comparative Example 2 and
Example 9 according to the invention) have the same
vanadium oxide, manganese oxide and cobalt oxide
contents and are characterized by an Rl ratio close to
1.5, but these oxides were added under different
conditions. Whereas this Rl ratio is particularly well
suited to the conditions in which the absorbent oxides
are added in the furnace, and makes it possible to
obtain a particularly neutral glass (Example 9), this
same ratio is, in this precise case, poorly suited to
the conditions in which the absorbent oxides are added
to the feeder, since Comparative Example 2 has a very
pronounced purple coloration characterized by very high
a* and b* values and a low LTC. In contrast, Example 10,
produced by feeder coloration, shows that a much lower
Rl ratio is much better suited to this method of
coloration.

Figure 1 shows the effect of manganese oxide on the Tuv
of glass compositions containing 0.09% Fe2O3 and 0.21%
V2O5 (Examples 2 and 3 according to the invention) . The
beneficial effect of manganese oxide in combination
with vanadium oxide may be observed. This beneficial
effect is surprising because only the decolorizing
effect of manganese oxide, which relies on absorption
in the visible range and not in the ultraviolet, was
known to those skilled in the art.

WE CLAIM;
1. Glass hollowware formed by molding, pressing or blowing, and
comprising a soda-lime-silicate glass composition, comprising the optical
absorbents below, in contents varying within the following weight limits:

wherein the glass has, for a thickness of 3 mm, an ultraviolet
transmission TUv, measured between 295 and 380 nm, not exceeding
40% and chromatic coordinates (a*,b*) under illuminant C of between -3
and +3.
2. The glass hollowware as claimed in claim 1, wherein the MnO content
is not less than 0.10%.
3. The glass hollowware as claimed in claim 1, further comprising cobalt
oxide (CoO) in a content not exceeding 0.0025%.
4. The glass hollowware as claimed in claim 1, wherein the V2O5 content
is not less than 0.16%.
5. The glass hollowware as claimed in claim 1, wherein the glass has, for
a thickness of 3 mm, an ultraviolet transmission not exceeding 20%.
6. The glass hollowware as claimed in claim 1, wherein the glass has, for
a thickness of 3 mm, a chromatic coordinate a* measured under
illuminant C of between -2 and 2.
7. The glass hollowware as claimed in claim 1, wherein the glass has, for
a thickness of 3 mm, a chromatic coordinate b* measured under
illuminant C of between 0 and 3.
8. The glass hollowware as claimed in claim 1, wherein the glass has, for
a thickness of 3 mm, a light transmission factor under illuminant C of
not less than 70%.

9. The glass hollowware as claimed in claim 1, comprising the coloring
agents below in contents varying within the following weight limits:

10. The glass hollowware as claimed in claim 1, comprising the coloring
agents below in contents varying within the following weight limits:

11. The glass hollowware as claimed in claim 1, wherein the redox state
of the glass does not exceed 0.2.
12. The glass hollowware as claimed in claim 1, including a glass matrix
comprising the following constituents (in percentages by weight):

13. A process for manufacturing the glass hollowware as claimed in
claim 1 and having an MnO/V2O5 ratio of between 1.2 and 1.8, the
process comprising melting the batch mix in a melting furnace, the said
batch mix providing all of the oxides in the composition, and forming
said glass to obtain hollowware.
14. A process for manufacturing the glass hollowware as claimed in
claim 1 and having an MnO/V2O5 ratio of between 0.5 and 1.2, the
process comprising melting part of the batch mix, transporting the
molten glass to the forming device, adding oxides during transporting to
said molten glass by glass fits or agglomerates, all of the vanadium and
manganese oxides, or the manganese oxide alone, being added to the
composition during this step, and forming said glass to obtain
hollowware.
15. The process as claimed in claim 14, wherein the MnO/V2O5 ratio is
between 0.8 and 1.2.
16. The glass hollowware as claimed in claim 1, wherein the MnO
content is not less than 0.13%.
17. The glass hollowware as claimed in claim 1, wherein the V2O5content
is between 0.19 and 0.22%.
18. The glass hollowware as claimed in claim 1, wherein the glass has,
for a thickness of 3 mm, a chromatic coordinate a* measured under
illuminant C of between 1 and 1.
19. The glass hollowware as claimed in claim 1, wherein the glass has,
for a thickness of 3 mm, a light transmission factor under illuminant C
of not less than 80%.
20. The glass hollowware as claimed in claim 1, wherein the redox state
of the glass does not exceed 0.1.

PATENT
TITLE: SODA-LIME-SILICATE GLASS COMPOSITION

ABSTRACT
The invention relates to a clear glass composition of
the soda-lime-silicate type that absorbs ultraviolet
radiation, which composition includes optical
absorbents below in contents varying within the
following weight limits:
Fe2O3 (total iron) 0.01 to 0.15%
V2O5 (total vanadium) 0.11 to 0.40%
MnO (total manganese) 0.05 to 0.40%
and which has, for a thickness of 3 mm, an ultraviolet
transmission not exceeding 40% and chromatic
coordinates (a*,b*) of between -3 and 3.
It also relates to glass hollowware or flat articles,
obtained from the aforementioned composition.